"Children who did not get vaccinated against whopping cough are one of the causes of the 2010 outbreak of the illness, when more cases were reported than in any year since 1947, researchers say."
"Researchers who looked at the geography of the cases suggest that clusters of 'nonmedical exemptions' to immunizations were one of several factors in the California outbreak. They reported their findings Monday in the journal Pediatrics.
In California in 2010, there were 9,120 cases of the illness that’s also called pertussis – one-third of all the U.S. cases. Los Angeles had 1,000 of those cases. Whooping cough is a respiratory ailment marked by bouts of coughing that are accompanied by a noise that can frighten parents – hence the name."